空的编辑文本给我0值错误

Question

I'm developing a project and I have problem with my addition for empty EditText( unused) . If I enter a number in my editText then click the button it will show the output in the viewtext (which is right) also if you keep doing that the number will be added to the total number .

BUT !! if I click the button without enter any number in my edittext . the project will be crashed showing the project has stopped !

What I want is : if I just click the button without enter any number the 0 will be added to the total number . ex.. 5 >> Button >> 5+0=5 show 5 for total >> 6 >> Button >> 6 + 5= 11 >> 0 >> Button >> 0 + 11 = 11 (<< KEY)

My code

MyActivity.java

    package b3du.im.myapplication;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;


public class MyActivity extends ActionBarActivity {


    int total = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my);
    }

    public void Add(View v){

        TextView text1 =  (TextView) findViewById(R.id.text1);
        EditText  text2 =  (EditText) findViewById(R.id.text2);


        int valueText2 = Integer.parseInt(text2.getText().toString());

        total= Integer.parseInt(text1.getText().toString());

        total += valueText2;

        text1.setText(Integer.toString(total));

        text2.setText("");

    }

}

activity_my.xml

<LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:gravity="center"
   >

    <TextView
        android:layout_width="50dp"
        android:layout_height="wrap_content"
        android:inputType="phone"
        android:ems="10"
        android:id="@+id/text1"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp"
        android:text="0"
        android:textSize="30dp"
        android:gravity="center" />

    <EditText
        android:layout_width="50dp"
        android:layout_height="wrap_content"
        android:inputType="number"
        android:ems="10"
        android:id="@+id/text2"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="20dp"
        android:hint="0"
        android:gravity="center" />

    <Button
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        android:id="@+id/button"
        android:layout_gravity="center_horizontal"
        android:onClick="Add" />
</LinearLayout>

Answer 1

If you enter nothing you get a blank in text2.getText().toString() and you get a NumberFormatException.

You should set `valueText2 to 0 if no text is entered:

int valueText2 = 0;

if (text2.getText() != null && !text2.getText().toString().equals("")){
   int valueText2 = Integer.parseInt(text2.getText().toString());

Answer 2

int valueText2 = Integer.parseInt(text2.getText().toString());

If the string is empty, parseInt will throw an exception. You need to check if its empty first and not vall parseInt.

Also, in the future always post the stack trace from logcat for a crash. It tells you exactly what the error is.